Method for providing and using information about inter-layer prediction for video signal

ABSTRACT

Disclosed is a method for providing and using information about inter-layer prediction when providing a video signal to a plurality of layers by encoding the video signal. The method for encoding an image signal to bit streams of an enhanced layer and a base layer, includes the steps of coding an image block in a picture of the enhanced layer into residual data based on image data of a block of the base layer corresponding to the vide block, and providing indication information through the bit stream of the enhanced layer, the indication information representing whether the coding is achieved in inter-layer prediction constraint or inter-layer prediction unconstraint.

TECHNICAL FIELD

The present invention relates to a method for providing and usinginformation about inter-layer prediction when providing a video signalto a plurality of layers by encoding the video signal.

BACKGROUND ART

According to a Scalable Video Codec (SVC) scheme, a video signal isencoded with a best video quality in such a manner that a low qualityvideo can be presented even though parts of picture sequences (framesequences intermittently selected from among the picture sequences)derived from the encoding are decoded. A motion compensated temporalfilter (or filtering) (MCTF) is one of encoding schemes suggested forthe SVC scheme.

However, although picture sequences encoded through the SVC scheme canpresent a low quality image even if only parts of received picturesequences are processed, image quality is seriously degraded if a bitrate is lowered. In order to overcome the image quality degradation, anadditional assistant picture sequence having a low transmission rate,such as a small-sized video and/or a picture sequence having the smallernumber of frames per second, may be provided in a hierarchy structurehaving at least one layer

On the assumption that two sequences are processed, an assistancesequence (a lower layer sequence) and a main picture sequence (an upperlayer sequence) are called a base layer and an enhancement layer,respectively. However, since the base layer and the enhanced layer areobtained by encoding the same video source, redundancy informationexists in video signals of both layers. Accordingly, in order to improvethe coding rate of the enhanced layer, the video signal of the enhancedlayer is coded using coding information of the base layer. This is oneof inter-layer prediction schemes.

For example, when the type of a current macro block in the enhancedlayer is determined as an intra mode macro block, the current macroblock is coded into residual data using image data of a correspondingblock in an intra mode of the base layer (this corresponding blocktemporarily simultaneous with and identical to the macro block of theenhanced layer).

The coded macro block is called an ‘intra BL mode block’, and thespecification of the intra BL mode for the macro block may be limited ornot. For example, as shown in FIG. 1A, the inter-layer prediction may beconstrained by allowing the inter-layer prediction only when thecorresponding block of the base layer is coded in the intra mode. Inaddition, as shown in FIG. 1B, the inter-layer prediction may not beconstrained by allowing the inter-layer prediction when thecorresponding block of the base layer is coded in an inter mode as wellas in an intra mode.

A encoding mode (in the side of an encoder) or a decoding mode (in theside of a decoder) is determined from one of modes shown in FIGS. 1A and1B based on the value of a ‘constrained_intra_pred_flag’ of the baselayer. When a macro block having residual data coded in an intra mode isreconstructed, this flag is used for indicating that a fixed value(constrained_intra_pred_flg=1) or a reconstructed pixel value(constrained_intra_pred_flg=0)) is employed for the adjacent inter modeblock.

However, when a video signal is encoded in three layers as shown in FIG.2, and when both the upper layer (L1) and the middle layer (L2) arecoded by employing the lower layer (L3) as a prediction layer and thenare provided to the decoder, both the upper layer (L1) and the middlelayer (L2) are constrained in a coding scheme for an intra mode block ofthe lower layer (L3). In other words, when theconstrained_intra_pred_flag of the lower layer (L3) is ‘1’,prediction-constraint is assigned to the upper layer (L1) and the middlelayer (L2) so that the upper layer (L1) and the middle layer (L2) arecoded through a constrained scheme as shown in FIG. 1A. In addition,when the constrained_intra_pred_flag is ‘0’, prediction-unconstraint isassigned to the upper layer (L1) and the middle layer (L2) so that theupper layer (L1) and the middle layer (L2) are coded through anunconstraint scheme as shown in FIG. 1B. In other words, wheninter-layer prediction is performed based on the lower layer (L3), theupper layers of the lower layer cannot individually select theinter-layer prediction constraint or the inter-layer predictionunconstraint.

In addition, since inter-layer prediction constraint (unconstraint) isdetermined for “constrained_intra_pred_flag” having a differentattribute, if the “constrained_intra_pred_flag” of a lower layer has aspecific value from among a plurality of layers, the upper layer mayloss the degree of freedom for the inter-layer prediction constraint. Inother words, only one of inter-layer prediction constraint andinter-layer prediction unconstraint is forcibly determined for the upperlayer.

DISCLOSURE OF INVENTION

Accordingly, the present invention has been made to solve theabove-mentioned problems occurring in the prior art, and an object ofthe present invention is to provide a method for transmittinginformation about inter-layer prediction constraint for a video signalthrough a prediction coded layer and decoding the video signal using thetransmitted information.

To accomplish the above objects, there is provided a method for encodingan image signal to bit streams of a first layer and a second layer, themethod comprising the steps of (1) coding an image block in a picture ofthe first layer into residual data based on image data of a block of thesecond layer corresponding to the vide block; and (2) providingindication information through the bit stream of the first layer, theindication information representing whether the coding is achieved ininter-layer prediction constraint or inter-layer predictionunconstraint.

According to another aspect of the present invention, there is provideda method for decoding encoded bit streams of a first layer and a secondlayer by receiving the encoded bit streams, the method comprising thesteps of: (1) determining indication information representing that allor a part of data of the first layer are coded in an inter-layerprediction constraint state or in an inter-layer prediction unconstraintstate, the indication information being provided through the bit streamof the first layer; and (2) determining whether an inter mode block ofthe second layer is reconstructed first or not in order to reconstruct acorresponding block having a specific mode in a picture of the firstlayer.

According to still another aspect of the present invention, there isprovided a method for decoding encoded bit streams of a first layer anda second layer by receiving the encoded bit streams, the methodcomprising the steps of: (1) determining indication informationindicating that use of adjacent inter mode block data is constrainedwhen an intra mode block is reconstructed, the flag being included inthe bit stream of the second layer; and (2) determining indicationinformation representing that all or a part of data of the first layerare coded in an inter-layer prediction constraint state or in aninter-layer prediction unconstraint state, the indication informationbeing provided through the bit stream of the first layer if thedetermined indication information of step (1) indicates that the use ofthe adjacent inter mode block data is constrained.

According to an embodiment of the present invention, the indicationinformation is allocated with different values depending on types ofpictures.

According to an embodiment of the present invention, the types of thepictures are classified into two types including a key picture (or apicture having a low band component) and a non-key picture (or a picturehaving a high band component).

According to an embodiment of the present invention, the indicationinformation is classified according to the types of the pictures and hasa value representing that the pictures are coded in an inter-layerprediction constraint/unconstraint.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1A is a view illustrating a scheme of predicting an intra modeblock based on a lower layer according to inter-layer predictionconstraint;

FIG. 1B is a view illustrating a scheme of predicting an intra modeblock based on a lower layer according to inter-layer predictionunconstraint;

FIG. 2 is a view illustrating an example of an inter-layer predictionscheme of upper layers when a video signal is encoded and transmittedthrough a plurality of layers including at least three layers;

FIG. 3 is a block diagram illustrating the structure of a video signalencoding device employing a scalable coding scheme for a video signalaccording to the present invention;

FIG. 4 is a block diagram illustrating the structure of a decoder fordecoding a data stream transmitted and encoded by the encoding deviceshown in FIG. 3;

FIG. 5 is a view illustrating an example of syntax used for determiningby a decoder whether or not inter-layer prediction is constrainedaccording to an embodiment of the present invention; and

FIG. 6 is a view illustrating an example of syntax used for determiningby a decoder whether or not inter-layer prediction is constrainedaccording to another embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription and drawings, the same reference numerals are used todesignate the same or similar components, and so repetition of thedescription on the same or similar components will be omitted.

FIG. 3 is a block diagram illustrating the structure of a video signalencoding device employing a video signal scalable coding schemeaccording to the present invention. Although the device shown in FIG. 3codes an input video signal in two layers, the following principle ofthe present invention is applicable between layers even if the devicecodes the input signal in three layers or more.

The video signal encoding device shown in FIG. 3 according to thepresent invention includes an enhanced layer (EL) encoder 1 for scalablyencoding an input video signal through a specification scheme (e.g.,MCTF or AVC) based on each macro block unit and generating suitablemanagement information, a texture coding unit 2 for converting theencoded information of each macro block into a compressed bit string, amotion coding unit 3 for coding motion vectors of a video block obtainedfrom the EL encoder 1 into a compressed bit string through a specificscheme, a base layer encoder 4 for encoding an input video signalthrough a specification scheme such as an AVC scheme and generating thesequence of small-sized videos, for example, the sequence of pictureshaving 25% of an original video size or the sequence of pictures havingthe same size as the enhanced layer and a low frame rate, a muxer 5 forencapsulating the output data of the texture coding unit 2, the encodedvideo sequence of the BL encoder 4, and an output vector data of themotion coding unit 120 in a predetermined format, multiplexing the datawith each other in a predetermined format, and then outputting themultiplexed data.

The EL encoder 1 performs a motion estimation operation and a predictionoperation with respect to a macro block in a predetermined image frame.In this case, the BL encoder 1 performs an inter-layer prediction codingusing video data and coding information provided from the BL encoder 4,inserts coding information according to the inter-layer predictioncoding as macro block information into a suitable header, and transmitsthe coding information if coding efficiency is improved.

In the coding procedure, if a current macro block to be coded isdetermined as an intra-mode macro block, it is determined that a blockcorresponding to the current macro block is in an intra-mode or in aninter-mode based on information provided from the BL encoder 4. In thecase of the intra-mode, the current macro block is specified as an intraBL mode block and coded into residual data using image data of thecorresponding block in the base layer.

In the case of the inter-mode, the current macro block may be specifiedas an intra BL mode block (in a case of unconstraint) according to aninter-layer prediction constraint/unconstraint state predetermined forencoding, and coded into the residual data using image data of thecorresponding block of the base layer as described above. In the case ofconstraint, the current macro block may be specified as an intra modeblock according to the inter-layer prediction constraint/unconstraintstate and coded into residual data based on pixel values of an adjacentmacro block.

In addition, in the case of constraint, specific information including“constrained_inter_layer_pred_flag” may be set to ‘1’. If the constraintis not set, the constrained_inter_layer_pred_flag may be set to ‘0’. Theset specific information is inserted into a header (a sequence header, apicture or picture group header, or a slice header) to be transmitted.

In the case of unconstraint, the EL encoder 1 codes an image of thecurrent macro block into residual data and specifies the mode of theimage of the current macro block as an intra BL mode based on areconstructed image obtained by performing a reconstruction operation(MC: Motion Compensation or inverse-MCTF) for an inter mode block of thebase layer corresponding to the current macro block. In thereconstruction operation for the inter mode block, the reconstructedimage may be received by requesting the image from the BL encoder 4,and, if the BL encoder 4 temporarily stores image data before thecurrent macro block is coded into the residual data, the stored imagedata may be used.

The EL encoder 1 may insert the constraint flag into one of severalheaders. If the EL encoder 1 inserts the constraint flag into a pictureheader (PPS; Picture Parameter Set and PPSE; PPS extension) or a sliceheader, the EL encoder 1 may specify inter-layer prediction constraintaccording to slices. In addition, the EL encoder 1 may insert theconstraint flag into a header for a sequence or a header for a group ofpictures (GOP) In this case, all slices belonging to the sequence or theGOP equally undergo constraint or unconstraint specified by theconstraint flag.

Description about encoding procedures for a macro block in several blockmodes will be omitted because the encoding procedures do not directlyrelate to the present invention. In addition, generally well-knownschemes may be employed for the encoding procedures.

Input image signals are stored in an additional storage unit throughencoding procedures including the above-described procedure. Then, allor a part of the image signals are read-out from the storage unitaccording to the request of a decoder and are transmitted through atransmission channel. The selection for an amount of the image signalsis determined according to the capacity of the transmission channel, anddescription about the selection for the amount of the image signals willbe omitted because the selection is regardless of the present invention.

FIG. 4 is a block diagram illustrating the structure of the decoder fordecoding a data stream encoded and transmitted as described above. Thedecoder shown in FIG. 4 includes a de-muxer 15 for dividing the receiveddata stream into a compressed motion vector stream and a compressedmacro block information stream, a texture decoding unit 12 forrecovering an original uncompressed information stream from thecompressed macro block stream, a motion decoding unit 13 for recoveringan original uncompressed stream from a compressed motion vector stream,an enhanced layer (EL) decoder 11 for converting the uncompressed macroblock information stream and the motion vector stream into an originalvideo signal through an MCTF scheme, and a base layer (BL) decoder 14for decoding base layer stream through a predetermined scheme such as anAVC scheme.

The BL decoder 14 provides header information included in an input baselayer stream to the EL decoder 11 while decoding the input base layerstream such that the EL decoder 11 can use required encoding information(in the header of the base layer stream) of the base layer includingmotion vector information and macro block mode information. In addition,the BL decoder 14 provides image data of the decoded base layer pictureor a picture, in which a part of blocks is decoded, to the EL decoder 11according to the direction of the EL decoder 11.

The EL decoder 11 determines the constrained_inter_layer_pred_flag,which is an inter-layer prediction constraint flag, in a header of a GOPor a sequence having a picture to be currently decoded among receivedpicture sequences of the enhanced layer. As described through the aboveencoding procedure, the inter-layer prediction constraint flag may bechecked in the picture header or the slice header.

If the inter-layer prediction constraint flag applied to a slice to bedecoded has been set as “inter-layer prediction constraint”(constrained_inter_layer_pred_flag=1), in the case of inter BL modeblocks in the slice, at least for intra mode blocks, the EL decoder 11receives decoded picture data provided by the BL decoder 14 (or readsthe decoded picture data from a memory shared between the EL decoder 11and the BL decoder 14) and reconstructs original image data fromresidual data of the intra BL mode block based on reconstructed data ofblocks in the decoded picture data corresponding to the intra BL modeblocks.

If the determined inter-layer prediction constraint flag applied to theslice to be decoded is specified as inter-layer prediction unconstraint(constrained_inter_layer_pred_flag=0), the EL decoder 11 directs the BLdecoder 14 to reconstruct all macro blocks in a slice of the base layercorresponding to the slice to be decoded and provide the reconstructedmacro blocks to the EL decoder 11. If the BL decoder 14 is set in such amanner that the BL decoder 14 always provides decoded data for allpictures, it is unnecessary for the EL decoder 11 to request thedirection according to conditions. However, since residual prediction isused between layers in addition to inter-layer prediction based on anintra BL mode, it is preferred that the BL decoder 14 reconstructs onlyintra mode block data instead of all data within a picture so as toprovide the reconstructed data to the EL decoder 11 and, if there isadditional direction, performs a reconstruction operation (the MC or theinverse_MCTF) for inter mode blocks within the picture so as to providea slice having the reconstructed image data.

The EL decoder 11 reconstructs original image data from residual data ofa current intra BL mode block based on reconstructed data of a blockcorresponding to the BL mode block in a slice having reconstructed datareceived from the BL decoder 14.

According to another embodiment of the present invention, informationabout inter-layer prediction constraint may be classified and setaccording to types of pictures.

If a type of a picture is a key picture or a picture coded using apicture having a low band component (an L picture in the case of theMCTF), the EL encoder 1 shown in FIG. 3 may set or reset flaginformation about “constrained_inter_layer_pred_L_flag”, therebytransmitting the flag information to the decoder. If the type of thepicture is a non-key picture or a picture coded using a high bandcomponent (an H picture in the case of the MCTF), the EL encoder 1 shownin FIG. 3 may set or reset flag information about“constrained_inter_layer_pred_H_flag”, thereby transmitting the flaginformation to the decoder.

The key picture denotes a picture coded into residual data by performinga prediction operation based on only a quality-base picture. Incontrast, the non-key picture denotes a picture coded into residual databased on SNR enhance picture data in addition to the quality-basepicture. The definition of the key picture is only one example, and thepresent invention is limited to the definition.

Although the two inter-layer prediction constrained flags(constrained_inter_layer_pred_L _flag and(constrained_inter_layer_pred_H_flag) are applied to different types ofpictures, the two flags have the same usage as theconstrained_inter_layer_pred_flag. Accordingly, the EL decoder 11 shownin FIG. 4 determines the value of theconstrained_inter_layer_pred_L_flag if a picture to be decoded is thekey picture or the picture having a low band component. If the pictureto be decoded is the non-key picture or the picture having a high bandcomponent, the EL decoder 11 determines the value of theconstrained_inter_layer_pred_H_flag. The reconstruction operation of aBL mode macro block according to the determined value is identical tothat of the previous embodiment of the present invention.

Hereinafter, another embodiment of the present invention will bedescribed.

When the constrained_intra_pred_flag, which indicates whether or notdata in an adjacent inter mode block are used in the reconstruction ofan intra mode block, is reset in the base layer, that is, when theconstraint is not set, the BL decoder 14 shown in FIG. 4 performs areconstruction operation through an MC scheme (an inverse-MCTF scheme)with respect to the adjacent inter mode block in order to reconstructresidual data in the intra mode block of the picture. In this case, itis advantageous that the EL encoder 1 shown in FIG. 1 encodes a macroblock to be encoded of the enhanced layer without distinguishing if ablock of the base layer corresponding to the macro block is in an intermode or an intra mode. Because, the EL decoder 11 shown in FIG. 4 canobtain reconstructed image data from the BL decoder 14 through theoperation such as the MC even for the inter mode block.

Accordingly, when the constrained_intra_pred_flag of the base layer isset to ‘0’ by the BL encoder 4 (that is, in a case in which constraintis not set with respect to the adjacent block), the EL encoder 1 shownin FIG. 1 transmits the constrained_inter_layer_pred_flag by resettingthe constrained_inter_layer_pred_flag or does not transmit theconstrained_inter_layer_pred_flag for a slice or a picture (a sequenceor a group including the slice or the picture) including a macro blockcoded in an intra BL mode.

Since constraint may be set or not for inter-layer prediction when theconstrained_intra_pred_flag of the base layer is set to ‘1’ (that is,data of the adjacent inter mode block are not used in the coding (orreconstruction) of the intra mode block due to the constraint set on theadjacent inter mode block), the EL encoder 1 codes a specific block toan intra BL mode block according to a predetermined predictionconstraint condition for the enhanced layer and transmits the specificblock by setting the constrained_inter_layer_pred_flag to ‘0’ or ‘1’. Ifconstraint is not set for inter-layer prediction in the case of theconstrained_intra_layer_pred_flag set to ‘1’, the EL decoder 11 requestsa reconstruction operation for the inter mode block from the BL decoder14 as described above according to the previous embodiment. Accordingly,in this case, the MC operation (or the inverse-MCTF) for datareconstruction must be performed in both layers.

In the meantime, as described above, according to the present invention,the EL decoder 11 shown in FIG. 4 determines whether or not constraintis set for inter-layer prediction through a scheme shown in FIG. 5because the constrained_inter_layer_pred_flag may not be transmittedfrom the encoder.

The EL decoder 11 initializes “interlayer_constrained” which is avariable for inter-layer prediction, as a unconstraint state value(i.e., ‘0’) and then determines the value of theconstrained_intra_pred_flag transmitted from the BL decoder 14. The ELdecoder copies the value of the constrained_inter_layer_pred_flagreceived through a header of the enhanced layer to the value of theinterlayer_constrained only if the value of theconstrained_intra_pred_flag has ‘1’.

The EL decoder 11 shown in FIG. 4 can recognize based on the value ofthe interlayer_constrained if constraint is set for inter-layerprediction. A procedure of reconstructing original image data fromresidual data of an intra BL mode macro block according to the state ofthe inter-layer prediction is identical to the procedure describedaccording to the previous embodiment.

In the meantime, it is selected whether or not constraint is set forinter-layer prediction according to the value of theconstrained_intra_pred_flag of the base layer, and information(constrained_inter_layer_pred_flag) indicating the selected constraintstate may be classified and allocated according to types of pictures.For example, the value relating to inter-layer prediction constraint maybe carried through the constrained_inter_layer_pred_L_flag whichcorresponds to a key picture or a picture coded using a low bandcomponent or the constrained_inter_layer_pred_H_flag which correspondsto a non-key picture or a picture coded using a high band component.

Although flag information classified according to types of pictures asdescribed above is used, both the flags may not be transmitted accordingto the value of the constrained_intra_pred_flag of the base layer or maybe transmitted with the value of ‘0’ or ‘1’ as described above. Inaddition, even the EL decoder 11 shown in FIG. 4 reconstructs an intraBL mode macro block according to the transmission state. If theconstrained_intra_pred_flag of the base layer has the value of ‘0’, andif the constrained_inter_layer_pred_L_flag, or theconstrained_inter_layer_pred_H_flag is not transmitted, the EL decoder11 shown in FIG. 4 performs an operation according to a syntax shown inFIG. 6 and determines whether or not the constraint is set forinter-layer prediction according to the final value of theinterlayer_constrained obtained through the operation.

Hereinafter, still another embodiment of the present invention will bedescribed.

Information about inter-layer prediction constraint may be deliveredusing one integrated indicator such as“constrained_inter_layer_pred_idc” without classification and allocationaccording to types of pictures as described according to the previousembodiment.

According to the present embodiment, theconstrained_inter_layer_pred_idc is set to ‘0’ when representing theconstraint inter-layer prediction regardless of the types of pictures.In addition, the constrained_inter_layer_pred_idc is set to ‘1’ whenrepresenting an inter-layer prediction unconstraint state for a firstpicture type (e.g., a key picture or a picture having a low bandcomponent), and an inter-layer prediction constraint state for a secondpicture type (e.g., a non-key picture or a picture having a high bandcomponent). The constrained_inter_layer_pred_idc is set to ‘2’ whenrepresenting the inter-layer prediction unconstraint state regardless ofthe types of pictures. The EL decoder 11 shown in FIG. 4 determineswhether or not constraint is set for the inter-layer predictionaccording to types of pictures based on the indication informationdepending on the indication value defined above.

According to the present embodiment, since there is rarely a procedureof encoding the first picture type in the inter-layer predictionconstraint state and the second picture type in the inter-layerprediction unconstraint state (actually, when the second type picture isencoded in the inter-layer prediction unconstraint state, it isunnecessary to encode the first type picture in the inter-layerprediction constraint state), the value indicating the case is excluded.However, it is natural that it is possible to represent the case byallocating the value of constrained_inter_layer_pred_idc with anadditional value such as ‘4’ if necessity.

As described above, a decoder of determining information representinginter-layer prediction constraint and performing a reconstructionoperation for a corresponding BL mode macro block according to thedetermination result (the reconstruction operation includes an operationof selectively reconstructing an inter mode block of a base layer basedon the information representing the inter-layer prediction constraint)may be installed at a mobile communication terminal or a device ofreproducing recorded media.

As described above, according to the present invention, the inter-layerprediction constraint/unconstraint state is directly delivered through aprediction-coded layer instead of a base layer for the inter-layerprediction, thereby individually setting or releasing predictionconstraint of each layer when a video signal is encoded and transmittedbased on a plurality of layers. Accordingly, coding can be freelyperformed, and layer coding suitable for an encoding environment can beachieved.

Although preferred embodiments of the present invention have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1.-15. (canceled)
 16. A method of decoding a video signal, comprising:obtaining inter-layer prediction constrained flag information indicatingwhether texture information of a corresponding block in a base layer isavailable for inter-layer prediction; obtaining the image information ofthe corresponding block based on the inter-layer prediction constrainedflag information; and decoding a current block based on the imageinformation and residual information, wherein the residual informationis difference value information between the current block in an enhancedlayer and the corresponding block in the base layer.
 17. The method ofclaim 16, wherein the inter-layer prediction constrained flaginformation is determined by a type of the current block.
 18. The methodof claim 16, wherein the inter-layer prediction constrained flaginformation is included in one of a slice header, a picture header, asequence header and a picture group header.
 19. The method of claim 16,wherein the corresponding block is coded by an intra mode.
 20. Themethod of claim 16, wherein the corresponding block is fullyreconstructed performing motion compensation.
 21. The method of claim16, wherein the current block is an intra BL mode.
 22. The method ofclaim 16, wherein the inter-layer prediction constrained flaginformation includes plural pieces of information being classified andallocated according to types of pictures.
 23. The method of claim 16,wherein the video signal is received as a broadcast signal.
 24. Themethod of claim 16, wherein the video signal is received on a digitalmedium.
 25. A computer-readable-medium comprising a program recordedtherein to execute the method of claim
 16. 26. An apparatus for decodinga video signal, comprising: a demuxer separating a compressed motionvector stream, a compressed macro block information stream and a baselayer stream from a received data stream; a texture decoding unitreconstructing the compressed macro block information stream into anuncompressed stream; a motion decoding unit reconstructing thecompressed motion vector stream into an uncompressed stream; a baselayer decoder decoding the stream of the base layer to obtain residualinformation for decoding current block; and an enhanced layer decoderobtaining image information of the corresponding block from the macroblock information stream and decoding the current block by the imageinformation, the motion vector stream and the residual information, theresidual information being provided from the base layer decoder, whereinthe inter-layer prediction constrained flag information indicateswhether image information of the corresponding block in the base layeris available for inter-layer prediction.
 27. An apparatus for encoding avideo signal, comprising: an enhanced layer encoder encoding an enhancedlayer according to a first scheme; and a base layer encoder encoding abase layer according to a second scheme; a texture coding unitcompressing the encoded information of a current block in the enhancedlayer; a motion coding unit compressing motion vectors in the enhancedlayer; and a muxer muxing the output data of the texture coding unit,the base layer encoder and the motion coding unit, wherein the enhancedlayer encoder sets inter-layer prediction constrained flag informationindicating whether image information of a corresponding block in thebase layer is available for inter-layer prediction into the bitstream.